1. Field of the Invention
The present invention relates to an apparatus and process for improved distribution of a liquid-vapor mixture through a bed of solid particles as the mixture flows generally downwardly toward the solid particles. More particularly, the present invention relates to an apparatus and process for improved distribution of a liquid-vapor mixture through a bed of solid catalyst particles in a hydrocarbon conversion process as the mixture flows generally downwardly toward the solid particles.
2. Description of the Prior Art
In any process which involves contacting a fluid with a bed of solid particles, good distribution of the fluid through the solid particles is important to effectively practice the process since poor distribution can lead to poor contact between the fluid and the solid particles. This is especially important where a two-phase fluid, i.e., liquid and vapor, stream flows through a bed of solid particles, such as, for example, in a hydrocarbon conversion process wherein a liquid-vapor mixed stream flows in a generally downwardly direction through a bed of solid catalyst particles. Good fluid distribution in such a system is important to effectively utilize the catalyst, since with poor distribution some of the flowing material may by-pass at least a portion of the catalyst, thereby reducing catalyst effectiveness. The prior art has recognized the need for good fluid distribution. See, generally, Hoftzer, Trans, Instn. Chem. Engrs. v. 42, T109 (1964); Ross, Chem. Engr. Progress, v. 61, #10, 77 (1965); and Schiesser and Lapidus, AICHEJ, v. 7, 163 (1961).
One distribution device of the prior art is similar to a bubble cap used in distillation equipment. This distributor includes a cap having slots at the lowermost portion thereof and around its entire periphery. The cap covers the upper portion of a hollow chimney which is, in turn, attached to a tray. The cap member of the distributor prevents the downflowing liquid-vapor stream from entering the top opening of the chimney directly. A plurality of such distributors is placed on the tray which is located upstream from the bed of solid particles through which the liquid-vapor stream is to be distributed. The liquid phase is deflected by the cap and flows downwardly onto the tray. When the level of liquid on the tray is sufficiently high, the liquid beings to flow through the slots and thence down the chimney to the space below the tray. The vapor phase flows directly through the slots and then down the chimney. The concurrent flow of liquid and vapor through the slotted area promotes mixing and distribution of the liquid and vapor.
One major disadvantage of this type of distributor is its sensitivity to the level of the supporting tray. Small deviations in the tray level can cause major differences in the quantity of liquid that flows through individual distributors disposed on the tray. Thus, this type of distributor can result in poor distribution of fluid through a bed of solid particles. Therefore, it would be advantageous to provide an apparatus and process for distributing a liquid-vapor mixture through a bed of solid particles. Also, it would be advantageous to provide a liquid-vapor distribution apparatus and process which has reduced sensitivity to the levelness of the distribution apparatus.